We are testing the hypothesis that the ingestion of preferred foods in humans will also release endogenous opiates which will be reflected in changes in pain threshold and/or changes in hedonic state as measured by self-report, facial expression, and left frontal EEG activation. Furthermore, we hypothesize that these changes will be naloxone reversible and that the degree of change in the pain and hedonic measures will differ in subjects who crave ice cream and those who do not crave ice cream.